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Deinonychus
These are similar in appearance to the Velociraptors, though Deinonychus are larger in size, though not as large as the Utahraptor. This 3.4 meter (11 ft) long dinosaur lived during the Early Cretaceous, about 115-108 million years ago. Fossils have been recovered from the U.S. states of Montana, Wyoming, and Oklahoma. They had a large claw on each foot that they could use to attack their prey. Scientists think they may have hunted in packs, not unlike modern wolves. It's tail contained ligaments and tendons that could keep the tail stiff so it could use it as a counterbalance. Due to their leg muscles and structure they could be said to be good at jumping and running. Description Paleontologist John Ostrom's study of Deinonychus in the late 1960s started the debate on whether dinosaurs were warm-blooded.Desmond A.J. 1977. The hot-blooded dinosaurs. ISBN 0-8600-7494-3 It is now accepted that all or most smaller theropods had feathers whose function was temperature regulation. Ostrom noted the small body, sleek, horizontal, posture, and—especially—the enlarged claws on the feet, which suggested an active, agile predator. Before this, the popular idea of dinosaurs had been one of plodding, reptilian giants.Bakker, Robert T. 1975. Dinosaur Renaissance, in Scientific American, April issue.Bakker, Robert T. 1986. The Dinosaur heresies: new theories unlocking the mystery of the dinosaurs and their extinction. Zebra Books. 'Deinonychus' means 'Terrible claw'. This refers to the large, sickle-shaped claw bone on the second toe of each hind foot. In life, archosaurs have a horny sheath over this bone which extends the length. Ostrom reconstructed the claw as over 4.7 in long. The species name antirrhopus means “counter balance”, which refers to Ostrom's idea about the function of the tail. As in other dromaeosaurids, the tail vertebrae have a series of ossified (bony) tendons and super-long bone processes. These features seemed to make the tail into a stiff counterbalance. A fossil of the very closely related Velociraptor mongoliensis has an articulated tail skeleton that is curved laterally in a long S–shape. This suggests that, in life, the tail could swish to the sides with some flexibility. Deinonychus remains have been found closely associated with those of the ornithopod Tenontosaurus. Teeth discovered associated with Tenontosaurus specimens imply it was hunted or at least scavenged upon by Deinonychus. History Fossil remains of Deinonychus have been found in the Cloverly Formation of Montana and Wyoming and in the Antlers Formation of Oklahoma, in North America. Additionally, teeth found in the Arundel Clay Facies of the Potomac Formation on the Atlantic Coastal Plain of Maryland may be assigned to the genus. The first remains were found in 1931 in southern Montana near the town of Billings. The team leader, paleontologist Barnum Brown, was primarily concerned to dig up and prepare the remains of the ornithopod dinosaur Tenontosaurus, but in his field report from the dig site to the American Museum of Natural History, he reported the discovery of a small carnivorous dinosaur close to a Tenontosaurus skeleton, "but encased in lime difficult to prepare." He informally called the animal "Daptosaurus agilis" and prepared to describe it and have the skeleton put on display, but never finished this work. Brown brought back from the Cloverly Formation the skeleton of a smaller theropod with seemingly oversized teeth that he informally named "Megadontosaurus". John Ostrom, reviewed this material decades later and realized that the teeth came from Deinonychus, but the skeleton came from a completely different animal. He named this skeleton Microvenator. In August 1964, John Ostrom led an expedition from Yale University’s Peabody Museum which found more skeletal material near Bridger. Expeditions during the next two summers dug up more than 1000 bones, among which were at least three individuals. Since the association between all the bones found was weak, which made it impossible to determine how many animals were present, the type specimen of Deinonychus was only the complete left foot and parts of right foot that definitely were from the same individual.Ostrom, J. H. (1969). [http://www.biodiversitylibrary.org/page/10658785#7 "Osteology of Deinonychus antirrhopus, an unusual theropod from the Lower Cretaceous of Montana"]. Peabody Museum of Natural History Bulletin 30: 1–165. The remaining specimens were catalogued in fifty separate entries at Yale's Peabody Museum of Natural History. Paleobiology Predatory behavior Deinonychus teeth found in association with fossils of the ornithopod dinosaur Tenontosaurus are quite common in the Cloverly Formation. In two quarries, Deinonychus fossils were found near Tenontosaurus fossils. The first, the Yale quarry in the Cloverly of Montana, includes numerous teeth, four adult Deinonychus and one juvenile Deinonychus. The collection of this number of Deinonychus skeletons in a single quarry suggests that Deinonychus may have fed on that animal, and perhaps hunted it. Ostrom and Maxwell have even speculated that Deinonychus might have lived and hunted in packs. (abstract) The second such quarry is from the Antlers Formation of Oklahoma. The site has six partial skeletons of Tenontosaurus of various sizes, as well as one partial skeleton and lots of teeth of Deinonychus. One tenontosaur arm bone even bears what might be Deinonychus tooth marks. Brinkman et al. (1998) point out that Deinonychus had an adult mass of 70–100 kilograms, while adult tenontosaurs were 1–4 metric tons. A solitary Deinonychus could not kill an adult tenontosaur, so pack hunting is possible.Brinkman, D. L.; R. L. Cifelli, and N. J. Czaplewski (1998). "First occurrence of Deinonychus antirrhopus (Dinosauria: Theropoda) from the Antlers Formation (Lower Cretaceous: Aptian–Albian) of Oklahoma". Oklahoma Geological Survey Bulletin 146: 1–27. A 2007 study by Roach and Brinkman has questioned the hunting behavior in groups of Deinonychus, based on what is known of modern carnivore hunting and the taphonomy of tenontosaur sites. Modern archosaurs (birds and crocodiles) and komodo dragons show little group hunts; instead, they are usually either solitary hunters, or are drawn to already killed carcasses, where much conflict occurs between individuals of the same species. For example, in situations where groups of komodo dragons eat together, the largest individuals eat first and will attack smaller komodos that try to feed; if the small animal is killed, it is cannibalized. When this information is applied to the tenontosaur sites, it seems that what is found is consistent with Deinonychus having a komodo- or crocodile-like feeding strategy. Deinonychus skeletons found at these sites are from young adults, with missing parts consistent with having been eaten by other Deinonychus. On the other hand, a paper by Li et al. describes track sites with similar foot spacing and parallel trackways, implying herd behavior of attack instead of uncoordinated feeding behavior. Bite force Bite force estimates for Deinonychus were first made in 2005, based on reconstructed jaw muscles. This study concluded that Deinonychus likely had a maximum bite force only 15% that of the modern alligator.Therrien, F., Henderson, D.M. and Huff, C.B. (2005). "Bite me: biomechanical models of theropod mandibles and implications for feeding behavior." Pp. 179–237 in Carpenter, K. (ed.), The Carnivorous Dinosaurs. Indianapolis: Indiana University Press. A 2010 study by Paul Gignac and colleagues attempted to estimate the bite force based directly on newly discovered Deinonychus teeth marks in the bones of a Tenontosaurus. These bite marks came from a large adult, and provided the first evidence that large Deinonychus could bite through bone. Using the tooth marks, Gignac's team were able to determine that the bite force of Deinonychus was significantly higher than earlier studies had estimated by biomechanical studies alone. They found the bite force of Deinonychus to be between 4,100 and 8,200 newtons, more than living carnivorous mammals including the hyena, and equivalent to a similar sized alligator. Gignac and colleagues also noted, however, that bone puncture marks from Deinonychus are relatively rare, and unlike larger theropods with many known puncture marks like Tyrannosaurus, Deinonychus probably did not often bite through or eat bone. Instead, they probably used their high bite force in defense or prey capture, not to feeding. Function of the claw Ostrom suggested that Deinonychus could kick with the sickle claw to cut and slash at its prey. Some researchers even think that it was used to claw the guts of large ceratopsian dinosaurs.Adams, Dawn (1987) "The bigger they are, the harder they fall: Implications of ischial curvature in ceratopsian dinosaurs" pg 1–6 in Currie, Philip J. and Koster, E. (eds) Fourth symposium on mesozoic terrestrial ecosystems. Tyrrell Museum, Drumheller, Canada Other studies have showed that the sickle claws may not have been used to slash but to give small stabs to their prey. Manning et al. (2005) ran tests on a robotic replica that precisely matched the anatomy of Deinonychus and Velociraptor, and used hydraulic rams to make the robot strike a pig carcass. In these tests the talons made only shallow holes and could not cut or slash. The authors tought that the talons would have been more effective in climbing than in dealing killing blows. Ostrom compared Deinonychus to the ostrich and cassowary. He noted that these birds can inflict serious injury with the large claw on the second toe. The cassowary has claws up to 4.9 in long. Ostrom cited Gilliard (1958) who said that they can cut off an arm or tear out a man's guts. Kofron (1999 and 2003) studied 241 documented cassowary attacks and found that one human and two dogs were killed, but no proof that cassowaries can rip apart other animals.Kofron, Chhristopher P. (1999) "Attacks to humans and domestic animals by the southern cassowary (Casuarius casuarius johnsonii) in Queensland, Australia Cassowaries use their claws to defend themselves, to attack threatening animals, and in agonistic displays such as the Bowed Threat Display. The seriema also has a large second toe claw, used it to tear up small prey items for swallowing. Biomechanical studies by Ken Carpenter in 2002 confirmed that the most likely function of the forelimbs to get prey was grasping, as their great lengths would have gave longer reach than for most other theropods. The large and elongated coracoid, indicating powerful muscles in the forelimbs, further strengthened this interpretation. Carpenter's biomechanical studies using bone casts also showed that Deinonychus could not fold its arms against its body like a bird ("avian folding"), contrary to what was inferred from the earlier 1985 descriptions by Jacques Gauthier and Gregory S. Paul in 1988.Paul, G.S. (1988). Predatory Dinosaurs of the World. New York: Simon and Schuster. pp. 366–369. ISBN 0-671-61946-2. Studies by Phil Senter in 2006 showed that Deinonychus forelimbs could be used not only for grasping but also to clutch things towards the chest. If Deinonychus had feathered fingers and wings, the feathers would have limited the range of motion of the forelimbs to some degree. For example, when Deinonychus extended its arm forward, the 'palm' of the hand automatically moved up. This would have caused one wing to block the other if both forelimbs were extended at the same time, leading Senter to conclude that clutching objects to the chest would have only been done with one arm at a time. The role of the fingers would also have been limited by feathers; for example, only the third digit of the hand could have been used in activities such as probing crevices for small prey, and only in a position perpendicular to the main wing. Alan Gishlick, in a 2001 study of Deinonychus forelimb mechanics, found that even if it had large wing feathers, the grasping ability of the hand would not have been significantly hindered; rather, but it would have been done perpendicular to the wing, and they would have held things with both hands at the same time in a "bear hug" way, findings which have been confirmed by the later studies by Carpenter and Senter. Parsons and Parsons have shown that juvenile and sub-adult specimens of Deinonychus show some morphological differences with the adults. For one thing, the arms of the younger specimens were proportionally longer than those of the adults, perhaps an indication of difference in behavior between young and adults. Another example of this could be the role of the claws of the hind legs. Parsons and Parsons have suggested that the claw curvature (which Ostrom 1976 had shown was different between specimens Ostrom, J.H. (1976). "On a new specimen of the Lower Cretaceous theropod dinosaur Deinonychus antirrhopus". Breviora 439: 1–21.) could have been greater for young Deinonychus, as this could help it climb in trees, and that the claws became straighter as the animal became older and started to live solely on the ground. This was based on the assumption that some small dromaeosaurids used their claws to climb. Deinonychus in The Land Before Time In the movies they are called Sharpteeth , but they may be called Fast Biters like their relatives. The Deinonychus were only seen in The Land Before Time VII: The Stone of Cold Fire, where six Deinonychus were seen attacking the herd that Pterano after the earthshake and before Littlefoot and the others goes to the great valley. It's not possible that most of the herd made it out of the ambush alive, although some could have escaped since some of the herd had weaponry to protect themselves. Gallery Screen Shot 2012-12-24 at 3.33.02 PM.png Screen Shot 2012-12-24 at 3.36.34 PM.png Screen Shot 2012-12-24 at 3.47.39 PM.png|Deinonychus File:LBT Deinonychus.jpg|thumb|Fast Biters VII File:Pack of Deinonychus.jpg|thumb|Deinonychus VII References Category:Fast Biters Category:Sharptooth Category:Twofooters Category:Dinosaurs Category:Antagonists Category:Villains Category:Land Before Time species